Х+49=6х-30+2х-12
х-6х-2х= -49-30-12
х-6х-2х= -91
7х-2х= -91
5х= -91
х= -91/5
х= -18,2
2x^2+3x-42+5x=0
2x^2+8x-42=0|:2
x^2+4x-21=0
по теореме Вието
x1+x2=-p=-4
x1*x2=q=-21
x1=-7
x2=3
9x^2-6x-24=0|:3
3x^2-2x-8=0
D=(-2)^2-4*3*(-8)=4+96=100=√100=10
x1=(-(-2)+10)/2*3=(2+10)/6
x1=2
x2=(-(-2)-10)/6=(2-10)/6=8/6
x2=1⅓
-0,5x²-x+4=0
Д=(-1)²-4*4*(-0.5)=1+8=9
x1=4
x2=-2